JPH114496A - Loudspeaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loudspeaker with superior heat resistance and acoustic characteristic by adopting a material which is superior in heat resistance and flexibility. SOLUTION: A composite material, consisting of a cloth of carbon fibers obtained by heat-treating polyacrylonitrile fibers in an active environment at a temperature of about 200-300 deg.C, so as to attain flame resistance, and a synthetic rubber such as a stylenebutadiene rubber is formed so as to obtain a loudspeaker edge having a carbon fiber cloth layer 12, a synthetic rubber layer 14 and a composite layer 13 of both the layers 12, 13. A groove 17 is formed to the synthetic rubber layer 14 consisting of a skin layer 15 and a foamed layer 16, and compliance of the edge is recovered by separating the edge from the groove 17 on the occurrence of a fire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker used for audio equipment and the like.
The present invention relates to a speaker having excellent heat resistance used as a speaker for disaster prevention.

[0002]

2. Description of the Related Art It is difficult to prevent a fire from spreading in a fire because a rubber-based material often used as an edge material of a speaker which emphasizes acoustic characteristics such as a high fidelity speaker has poor heat resistance. Therefore, the edge materials of speakers for special applications such as speakers for disaster prevention emphasize heat resistance, inorganic materials such as metals and glass fibers, engineering plastic films such as polyarylate and polyethersulfone, cotton and polyamide. A material in which a base fabric such as a fiber is impregnated with a thermosetting resin such as a phenol resin is used.

[0003]

However, since these conventional heat-resistant edge materials lack flexibility, the sound pressure-
It is difficult to control the lowest resonance frequency (f ₀ ) in the frequency characteristics to the lower frequency side, and the internal loss is low, so that flat frequency characteristics cannot be obtained. Has not been obtained sufficiently well.

[0004] The present invention has been made in view of such circumstances, and has as its object to provide a speaker having excellent heat resistance and having a preferable edge also from the viewpoint of acoustic characteristics.

[0005]

In order to achieve the above object, a loudspeaker according to the present invention has an edge formed by molding a composite sheet comprising a cloth of carbon fiber obtained by oxidizing polyacrylonitrile fiber and synthetic rubber. It is characterized by doing.
With such a configuration, a speaker having edges having both heat resistance and flexibility and having good heat resistance and acoustic characteristics is provided. Here, the term “flame resistance” refers to a process of heating to about 200 to 300 ° C. in an active atmosphere such as air. By this treatment, the ladder polymerization due to the formation of a naphthyridine ring proceeds through the oxidation step, and the fiber is made flame-resistant.

In the above-mentioned speaker, the edge formed by forming a multilayer composite sheet including a layer made of carbon fiber cloth, a layer made of carbon fiber cloth impregnated with synthetic rubber, and a layer made of synthetic rubber is formed as described above. It is preferable to arrange the carbon fiber layer so as to be the outermost surface layer on the diaphragm opening side. With such a configuration, while the carbon fiber cloth and the synthetic rubber are integrally combined, the synthetic rubber layer relatively weak to heat is protected by the layer made of the carbon fiber cloth strong to heat. The heat resistance of the edge is further improved. Such a configuration is particularly suitable for 600 to 100 supposed in an actual fire.
This is effective in improving heat resistance when the edge is directly exposed to a flame of about 0 ° C.

In the speaker, it is preferable that the synthetic rubber layer has a structure in which a foam layer is sandwiched between skin layers. By adopting such a configuration, the edge is reduced in weight and the apparent rigidity is also improved.
The acoustic characteristics of the speaker are further improved. Here, the skin layer is a layer substantially free of foaming formed on the surface of the synthetic rubber layer.

In the speaker, it is preferable that the edge is provided with a reduced strength portion so that a slit is formed at the edge by a stress generated by heating. With such a configuration, it is possible to reduce the tension of the edge caused by the contraction of the synthetic rubber in a high-temperature environment. If the tension state of the edge is reduced, it is possible to suppress the deterioration of the acoustic characteristics of the speaker in the low frequency range. However, the strength-reducing portion does not need to be formed excessively, and is preferably provided in a range that does not affect the sound reproduction characteristics in a normal use state.

[0009] Further, the strength-reduced portion is, specifically,
It is preferable to include a groove formed on the surface of the edge. In addition, it is preferable that the reduced strength portion is arranged so that there is no strong bias in the edge so that the voice coil bobbin can accurately perform the piston movement even when the slit is formed, and it is not necessarily limited. However, for example, it is preferable that they are arranged at substantially equal intervals on the edge.

It is preferable that a heat-resistant cloth is provided on the edge so as to cover the reduced strength portion.
With this configuration, even if a slit is formed in the edge due to heating, it is possible to prevent the flame from entering the slit. It is preferable that the heat-resistant cloth be disposed on the edge surface in a bent state in anticipation of cracking due to heating of the reduced strength portion.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a sectional view showing an embodiment of the composite sheet of the present invention. Synthetic rubber is impregnated from the surface of the carbon fiber cloth, and the carbon fiber cloth and the synthetic rubber are integrated by the layer 3 in which the carbon fiber cloth and the synthetic rubber are combined. The synthetic rubber impregnates only a part of the carbon fiber cloth, and the remaining layer is the carbon fiber cloth layer 2. Further, the synthetic rubber is not entirely impregnated, but the synthetic rubber not impregnated forms the synthetic rubber layer 4 adjacent to the composite layer 3. Since the ratio of the thickness of each layer has a subtle effect on the acoustic characteristics of the speaker, it is preferable to appropriately change the ratio depending on the usage.

The carbon fiber cloth can be obtained by heat-treating polyacrylonitrile fibers in air at 200 to 300 ° C. The polyacrylonitrile fiber is usually finally heat-treated at a high temperature of 1200 to 1400 ° C. in an inert gas and used as a PAN-based carbon fiber. However, the carbon fiber obtained in this way is excellent in strength and heat resistance, but is too rigid. Since the edge material compliance of a speaker is a very important factor in sound quality, it is preferred that the edge material be flexible. Since the edge shape also affects the sound quality, it is preferable that the edge material has excellent moldability. Therefore, the carbon fiber treated at the high temperature is not suitable as a speaker edge material from the viewpoint of acoustic characteristics and moldability. The present inventors have found that carbon fibers obtained by flame-resistant polyacrylonitrile fibers have both heat resistance and flexibility, and are particularly suitable as edge materials for speakers.

The carbon fiber may be used as a woven fabric, but is preferably used as a nonwoven fabric because the same physical properties are always obtained in the circumferential direction without changing the compliance in the weft direction. By using a nonwoven fabric, it is possible to suppress acoustic distortion caused by inhibiting a resonance mode caused by a partial decrease in strength and accurate piston movement of the diaphragm.

Further, the areal density of the carbon fiber cloth used is as follows:
20 to 60 g / m ² is preferred. When the areal density is 20 g / m ² or more, shape retention performance during heating is improved, and when the areal density is 60 g / m ² or less, moldability of the composite sheet is improved.

As the synthetic rubber, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NB)
R), diene rubbers such as chloroprene rubber (CR),
Alternatively, even if it is a non-diene rubber, ethylene propylene rubber (ethylene propylene copolymer (EPM) or ethylene propylene diene terpolymer (EPDM)) or the like can be used. In order to further improve the heat resistance and flame resistance of the edge, it is preferable to add 5 to 10% by weight of an antimony oxide, a halogen-based or a phosphorus-based additive to these synthetic rubbers.

When compounding a carbon fiber cloth and synthetic rubber, the cloth is impregnated with synthetic rubber so that the carbon fibers act as an aggregate so that the edges are hardly deformed when the rubber is deteriorated by heating. Is preferred. Although the whole may be a composite layer, it is preferable from the viewpoint of protection of the synthetic rubber to form a multilayer structure by partially impregnating the carbon fiber cloth with the synthetic rubber layer as described above. Examples of such a multilayer structure are shown in FIGS. 1 and 2,
The present invention is not particularly limited to these embodiments. For example, an embodiment may be adopted in which a carbon fiber cloth layer sandwiches a synthetic rubber layer.

The composite edge material 1 is formed into a desired speaker edge shape by means such as thermal compression molding in a mold. At the time of this molding, if the synthetic rubber is a thermal crosslinking type, a crosslinking reaction can be performed simultaneously with molding by heating during molding. Therefore, if heat compression molding is performed by bringing the carbon fiber cloth and synthetic rubber into contact with each other, the composite of the edge material and the molding into the edge can be performed in the same step. In order to employ such an efficient production method, it is preferable to use a synthetic rubber of the present invention which is made into a thermal cross-linking type by adding a sulfur component or the like.

(Second Embodiment) FIG. 2 is a sectional view showing an edge material according to another embodiment of the present invention. The edge material 5 shown in FIG. 2 can be manufactured by adding a foaming agent to synthetic rubber and performing the same heat compression molding as described above. In this manner, foaming is started at the time of molding to form a foamed layer 10, and a skin layer 9 without foaming is formed on the surface of the synthetic rubber in contact with another material. Since the foamed layer 10 has a sandwich structure sandwiched between the skin layers 9 and is lightweight and has improved apparent rigidity, the edge formed by the edge material 5 shown in FIG. And unnecessary resonance of the diaphragm can be suppressed.

As the foaming agent, ADCA (azodicarbonamizo) foaming agent, DPT (dinitropentamethylenetetramine) foaming agent, OBSH foaming agent and the like can be used.

(Third Embodiment) FIG. 3 is a sectional view of an edge material according to still another embodiment of the present invention. A groove 17 is provided in the synthetic rubber layer 14 of the edge material 11 shown in FIG. The groove 17 can be formed by providing a protrusion on a mold when performing thermocompression molding using, for example, the same method as in the second embodiment. FIG. 4
Is an edge 18 formed using such an edge material.
FIG. 5 is a diagram showing an example of the back side (from the inside of the speaker). In the ring-shaped edge 18 shown in FIG. 4, three groove portions 17 are formed so as to be at equal intervals (so that the line connecting the center of the ring and each groove portion keeps an interval of 120 °).

When heated in a fire, the synthetic rubber shrinks due to its change in molecular structure. This shrinkage causes internal stress at the edge, but in a typical embodiment, this internal stress will not be large enough to exceed the tensile strength of the edge. However, this stress has such a magnitude that the edge can be cut off from the portion where the strength is reduced inside the edge. In the present embodiment, a slit is formed intentionally at the edge using this stress.

The shrinkage of the synthetic rubber used for the edge has an undesirable effect on the reproduction characteristics of the speaker after a fire has occurred. Flexibility is lost and compliance is reduced. However, according to the present embodiment, since the slit is formed in the edge and the tension state of the edge is relaxed, the compliance that is reduced in the material characteristics is recovered by the structural change of the edge. Due to such a change, specifically, the amplitude amount of the diaphragm of the speaker is recovered, so that the acoustic characteristics of the speaker particularly in a low frequency range are improved.

The groove 17 is formed so as to reduce the strength of the edge to such an extent that the edge is split from that portion by the stress generated at the edge in a high temperature environment. Therefore, as long as this purpose can be achieved, the shape and depth of the groove
It is not limited to the illustrated one. For example, the cross-sectional shape of the groove 17 is not limited to a rectangular shape as illustrated,
It may have a semicircular shape or the like. It is not necessary to form the groove as a continuous groove. For example, the groove may be a perforated groove formed intermittently. Further, such a reduced strength portion may be formed in a layer other than the synthetic rubber layer 14. For example, if a perforation is formed in the carbon fiber cloth, the perforated portion becomes a portion where the strength is reduced. In addition, it is preferable that the strength-reducing portion such as a groove is generally formed in a direction crossing the edge as shown in the figure.

As described above, the shape of the reduced strength portion of the present invention is not particularly limited. However, in consideration of an actual fire, when the edge is heated from room temperature to 200 to 300 ° C., the strength is reduced. It is preferable to form the slit so that the edge is cleaved from the portion to form a slit.

The reduced-intensity portions are preferably arranged systematically, for example, as described above, so that the edges can be evenly divided. If the slits are locally concentrated, the voice coil bobbin or the coil wire may come into contact with the top plate or the yoke in the gap of the magnetic circuit, and the speaker may be damaged. Also,
The number may be determined as appropriate from various conditions such as the edge shape. For example, in the case of a typical edge shape as shown in FIG. If formed excessively, the tension at the time of heating is dispersed, and there is a possibility that the tension necessary for forming the slit does not act on all the portions where the strength is reduced. Although the deformation itself due to the shrinkage of the synthetic rubber is not uniform in nature, the uniformity of the shrinkage of the synthetic rubber layer 14 is reduced if the layer 13 in which the carbon fiber cloth and the synthetic rubber are combined as shown in FIG. Be improved. Such uniformity of edge contraction is preferable for forming a plurality of slits in a planned manner.

[0026]

EXAMPLES The following four types of edges were prepared. A. The polyacrylonitrile fiber which was steamed in a furnace maintained at 250 ° C. was processed into a nonwoven fabric having an areal density of 35 kg / m ² . A sheet of a thermo-crosslinkable styrene-butadiene rubber is placed on one side of the surface of the carbon fiber nonwoven fabric and placed in a mold at 200 ° C. for 1 minute at 50 kg / cm ^2.
The material was compounded by thermocompression molding under the pressure described above, and the shape of the edge of the speaker was obtained. B. An edge was produced in the same manner as in A except that 5% by weight of an azodicarbonamizo-based blowing agent and 5% by weight of antimony trioxide and a halogen-based flame retardant were added to styrene-butadiene rubber. C. An edge was produced in the same manner as in A except that no carbon fiber nonwoven fabric was used. D. After filling the cotton woven fabric with phenolic resin,
A coating of a styrene-butadiene rubber / acrylonitrile-butadiene rubber mixed latex as a coating agent was subjected to thermal compression molding at 200 ° C. for 30 seconds at 100 kg / cm ² to produce an edge.

When the cross sections of the edges A and B of these edge materials were confirmed, they were the same as those shown in FIGS. 1 and 2, respectively. At both edges of A and B, the carbon fiber nonwoven fabric is impregnated with the styrene-butadiene rubber melted by the heat at the time of the heat compression molding. It has a multi-layer structure. Further, the edges A and B were firmly adhered to each other by impregnation with a synthetic rubber, and were composited.

Next, approximately 600 to
A burner flame of 700 ° C. was irradiated for 10 seconds. At this time, the flames of the edges A and B were irradiated from the side of the carbon fiber nonwoven fabric. Table 1 shows the obtained observation results.

(Table 1)-----------------------------------------------------------------------------------------------------Edge −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− A 5 seconds later, the rubber material on the back side was ignited, but it did not burn out and B Ignition C Ignition and burning in 2 seconds D Ignition and burning in 2 seconds --------------------------------------------------------------------- −

The edges A and B maintain their shapes after the flame irradiation, and have improved heat resistance and flame resistance as compared with the conventionally used edge C or cloth edge D of synthetic rubber alone. Was confirmed.

Next, the internal loss of the edges B and D was measured by the vibration reed method. Table 2 shows the results. Edge B
Has been confirmed to be larger than the internal loss at the edge D.

(Table 2) −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Edge Internal loss (tan δ) −−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− B 0.315 D 0.135 −−−−−−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−

Further, a speaker as shown in FIG. 5 was completed by incorporating the edges of edges A, B and D, and the sound pressure frequency characteristics of these speakers were measured. The results are shown in FIGS. When the edges A and B were incorporated, the carbon fiber cloth layers 2 and 6 were arranged so as to be the outermost surface on the opening side of the diaphragm 22 (upper in FIG. 5).

6 to 8, the flatness of the sound pressure frequency characteristic is improved at the edges A and B as compared with the cloth edge D, and the second harmonic distortion and the third harmonic distortion are reduced. It was confirmed that. In addition, since the edge B including the foam layer inside is lighter than the edge A, the sound pressure is improved.

Further, the following two types of edges were prepared. E. FIG. On the surface of the synthetic rubber layer, three grooves having a depth of half the thickness of this layer are formed so as to traverse the synthetic rubber layer from the ring center of the ring-shaped edge to the outer peripheral side so that they are equally spaced from each other. The edges were made as in B except that they were formed (to make an angle of 120 °). The groove was formed by a protrusion provided on an edge molding die. In addition, when the cross section and the back surface of the edge E were confirmed, they were the same as those shown in FIGS. F. An edge was formed on the surface of the synthetic rubber layer in the same manner as in E, except that the carbon fiber woven fabric was bonded using a heat-resistant adhesive so as to cover the groove in a state where the carbon fiber woven fabric was bent. The cross section of this edge was similar to that shown in FIG.

Next, incorporating the edges B, E and F,
A speaker as shown in FIG. 5 was completed. These speakers are placed in a closed electric furnace at the opening side of the diaphragm 22 (FIG. 5).
(Upper part in FIG. 2) faces the inside of the electric furnace. The diaphragm 22 was covered with a heat insulating material so that heat did not directly hit the diaphragm 22. The temperature inside the electric furnace was set to be maintained at 500 ° C., and left for 15 minutes while a 1 W music signal was input. After standing, the sound pressure frequency characteristics of the speaker incorporating the edges B and E were measured. FIG. 9 shows the obtained acoustic characteristics.
And FIG. In addition, when the speaker using the edges E and F was observed, it was confirmed that the edge was cleaved from the groove and three fine slits were formed.

As shown in FIG. 9 and FIG.
In (2), since the edge material is contracted and hardened by heat, the amplitude cannot be secured, the low-frequency reproduction characteristics are deteriorated, and the sound pressure is also reduced. On the other hand, at the edge E, a slit is formed, and compliance is maintained mechanically and structurally, so that the amplitude amount can be maintained, and low-frequency reproduction and sound pressure can be maintained. I have. Table 3 shows the lowest resonance frequency and the sound pressure of the edge B and the edge E.

(Table 3) −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Lowest resonance frequency (f ₀ ) Sound pressure −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Edge B 2000Hz 85dB Edge E 220Hz 90dB −−−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−− The sound pressure in Table 3 is the sound pressure at each lowest resonance frequency (f ₀ ).

With the speaker incorporating the edge F, almost the same acoustic characteristics as those obtained when the edge E was used were obtained. Further, the speaker incorporating the edge F had its edge cross section changed to the state shown in FIG. 12 after heating. Since the gap of the slit 28 grown from the groove 27 is covered by the carbon fiber cloth 29 bonded to the edge 25, this edge can prevent the flame and heat from the front face from directly entering through the slit 28. Has become.

As described above, the edges A and B are superior to the cloth edge D, which is a conventional heat-resistant edge, in heat resistance under severe conditions assuming an actual fire in which a surface is directly irradiated with a flame. In addition, it was also found that, in terms of acoustic characteristics, among the heat-resistant edges, the edge is superior to the edge D which is flexible. Further, the edges E and F can suppress the lowering of the low-frequency reproduction characteristic and the sound pressure characteristic even when the flexibility of the edge material is reduced by heat. It was found that the characteristics could be restored to about the same level as before.

[0041]

As described above, according to the present invention,
Heat resistance and acoustic properties are obtained by using an edge obtained by molding a sheet obtained by compounding a heat-resistant and flexible carbon fiber obtained by oxidizing polyacrylonitrile fiber with a synthetic rubber having excellent flexibility. Thus, it is possible to provide an excellent speaker.

The edge formed by forming a multilayer composite sheet including a layer made of carbon fiber cloth, a layer made of carbon fiber cloth impregnated with synthetic rubber, and a layer made of synthetic rubber is attached to the layer made of the carbon fiber cloth. Is arranged so as to be the outermost surface layer on the diaphragm opening side, thereby improving heat resistance particularly when the edge is directly exposed to a flame.

Further, since the synthetic rubber layer has a structure in which the foam layer is sandwiched between the skin layers, the edges are reduced in weight and the apparent rigidity is improved, so that the acoustic characteristics of the speaker are further improved.

Further, by forming a structure in which the edge is provided with a reduced strength portion such as a groove so that a slit is formed in the edge due to stress generated by heating at the time of fire, the edge material is heated and becomes flexible. Loss of sound, the compliance can be structurally restored, and low-frequency reproduction and deterioration of sound pressure can be suppressed. Furthermore, even if a slit is formed, it is possible to prevent a flame or heat from directly entering the inside of the speaker by forming a structure in which a heat-resistant cloth is provided on the edge so as to cover the reduced strength portion. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an edge material according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the edge material according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the edge material according to the present invention.

FIG. 4 is a bottom view (back view) of an edge according to the present invention.

FIG. 5 is a sectional view showing one embodiment of a speaker according to the present invention.

FIG. 6 is a sound pressure-frequency characteristic diagram of an edge A.

FIG. 7 is a sound pressure-frequency characteristic diagram of an edge B.

FIG. 8 is a sound pressure-frequency characteristic diagram of an edge D.

FIG. 9 is a sound pressure-frequency characteristic diagram of the edge B after a heat resistance test.

FIG. 10 is a sound pressure-frequency characteristic diagram of the edge E after a heat resistance test.

FIG. 11 is a sectional view showing another embodiment of an edge according to the present invention.

12 is a cross-sectional view showing a state after heating the edge shown in FIG. 11;

[Explanation of symbols]

 1, 5, 11 Edge material 2, 6, 12 Carbon fiber cloth layer 3, 7, 13 Carbon fiber-rubber composite layer 4, 8, 14 Synthetic rubber layer 9, 15 Synthetic rubber skin layer 10, 16 Synthetic rubber foam layer 17, 27 Groove 21 Edge 22 Diaphragm 23 Frame 28 Slit 29 Heat-resistant woven fabric 31 Speaker

Claims (7)

[Claims] 1. A loudspeaker having an edge formed by molding a composite sheet comprising a carbon fiber cloth obtained by oxidizing polyacrylonitrile fiber and a synthetic rubber. 2. An edge formed by molding a multilayer composite sheet having a layer made of carbon fiber cloth, a layer of carbon fiber cloth impregnated with synthetic rubber, and a layer made of synthetic rubber is formed from the carbon fiber cloth. 2. The loudspeaker according to claim 1, wherein said layer is arranged to be the outermost layer on the diaphragm opening side. 3. The speaker according to claim 2, wherein the layer made of synthetic rubber has a structure in which a foam layer is sandwiched between skin layers. 4. The loudspeaker according to claim 1, wherein the edge is provided with a reduced strength portion such that a slit is formed at the edge by a stress generated by heating. 5. The speaker according to claim 4, wherein the reduced strength portion includes a groove formed on a surface of the edge. 6. The loudspeaker according to claim 4, wherein the reduced intensity portions are arranged at substantially equal intervals on the edge. 7. The loudspeaker according to claim 4, wherein a heat-resistant cloth is provided on the edge so as to cover the reduced strength portion.